The invention discloses a large-span self-anchored type suspension bridge system conversion method. The method comprises the following steps that suspension bridge permanent towers, side piers, auxiliary piers, temporary brackets and temporary cable-stayed bridge steel towers are constructed; the junctions of the towers and beams serve as operating platforms, and side span construction is conducted till side spans are folded; main beams are spliced in a suspension mode by using hanging cables and buckle cables on the temporary cable-stayed bridge steel towers till middle spans are folded; stay cables are stretched, and the line shapes of the main beams are lifted to be close to the line shape of a suspension bridge dismantling the two-phase constant load; catways and a traction system are constructed, and a main cable is erected; hanging cables are stretched till all the hanging cables are mounted; the stay cables and the temporary cable-stayed bridge steel towers are dismantled; and the two-phase constant load is added, and cable force of the hanging cables is subjected to fine adjustment. According to the large-span self-anchored type suspension bridge system conversion method, the amount of extension rods and the number of stretching equipment are reduced, and meanwhile frequency of stretching circulation is reduced.